I don't mute my mic and I always check to see if a random has entered chat mode. One time I accepted a random invite from a lower ranked player on Mars. I don't usually do that. He was doing one of the story missions. I had entered team chat but there was nothing so I didn't say anything either. We played through the entire mission not talking. At the end I sighed and the other guy (a 13 year old) said, "Wait. You have a mic active"!. He was actually pretty cool. He said thanks and exited the fireteam. I was surprised, he hasn't squeaked once.